1. Field of the Invention
The present invention relates generally to a filtering method and an apparatus of a low complexity Finite Impulse Response (FIR) filter, and a recording medium thereof. More particularly, the present invention relates to a filtering method and an apparatus of a low complexity FIR filter applicable regardless of a filter order by simplifying computations, and a recording medium thereof.
2. Description of the Related Art
Various digital audio, voice, and video electronic devices including mobile communication terminals get rid of noise using a spectrum shaping or a signal scheme. A filter mostly frequently used to remove the noise of the digital electronic device is a Finite Impulse Response (FIR) filter.
The FIR filter has a FIR function h(n), which is expressed as a N-th order polynomial.
Provided that an input signal fed to the N-th order FIR filter is x(n) and its output signal is y(n), the output signal y(n) for the input signal x(n) can be defined by the response function h(n) of the FIR filter as follows:
                              y          ⁡                      (            n            )                          =                              ∑                          k              =              0                                      N              -              1                                ⁢                                    h              ⁡                              (                k                )                                      ⁢                          x              ⁡                              (                                  n                  -                  k                                )                                                                        (        1        )            
In Equation (1), h(k) is a filter coefficient, N is a filter order (or tap number) a filter input, and y(n) is a filter output. The operation of the FIR filter based on Equation (1) performs the multiplication for N times by matching the input signals and the filter coefficients one to one and sums up the products. As a result, as the filter coefficients increase, more multipliers and additions are required and the computations also increase.
More specifically, in the signal processing for the audio, the voice, and the video, the computations of the FIR filter take up the audio, voice and video codec computation. Further, in the computation of the audio, voice, and video codec, when the conventional FIR filter as discussed above is used, the filter structure becomes complicated and its computations considerably increase.